In some cases, a mixed oxide X Y oxide can be contrasted with a compound X Yate.
In most cases, common sense can prevail.
For example, the compound sodium nitrate is not described as 'sodium nitrogen oxide'; even less so, would it be called 'nitrogen sodate'. With this, we have some common sense, that the compound is a nitrate, not a 'sodate', and not even a mixed oxide.
In some cases, the conclusion is not so obvious. For example, some compounds are called 'titanates'; are these 'titanates', or maybe X titanium oxides? In this case, the result depends on some knowledge of structure: in general, Xates have the Xate ion; a mixed oxide will not have such.